1. Field of the Invention
This invention generally relates to printing presses and particularly to apparatus for mounting a plurality of oscillating rollers while selectively allowing only some to engage in pivotal movement.
2. Description of the Related Art including Information Disclosed under 37 CFR 1.97-1.99
It is known in offset printing presses which carry a printing plate on a rotating plate cylinder to oscillate the form rollers in direct contact with the plate cylinder in their elongate axial direction to more evenly distribute the application of ink liquid, or dampening liquid, over the surface of the plate. This liquid is obtained from a source of liquid including in the roller train, such as a fountain reservoir, a dampener fountain roller in contact with the liquid in the reservoir and a brush roller in contact with the fountain roller to brush dampening liquid in a spray or mist directly onto the first of a train of rollers and drums. In a shortened dampener train, the first roller to receive the dampening liquid is a gear driven, rotating drum roller with an outer surface. This drum roller is in contact with a transfer roller which is nonoscillating. The nonoscillating transfer roller, in turn, is in contact with a nonoscillating, gear driven, elongate drum roller to convey or transfer liquid from the drum roller, which receives the liquid directly from the source, to an outer surface of the elongate drum roller. The elongate drum roller then conveys it to the surface of the oscillating form roller.
The form roller is mounted for oscillating movement by mounting it for rotary movement relative to a mounting bracket and then oscillating the bracket. In addition to being mounted for oscillatory movement, the form roller is also mounted for adjustment of its pivotal position relative to the rotary axis of the elongate drum roller in order to vary the amount of pressure between the plate cylinder and the form roller.
While this known dampener system is satisfactory, it also suffers from ghosting in which an image from a prior print in the cycle is reprinted offset from the primary image such that a "ghost" image appears.